The invention applies generally to the management of bearer services in a third generation mobile telecommunications system. Especially the invention applies to the establishment and upkeep of bearers for services that have different quality of service requirements between a mobile station and the fixed parts of the mobile telecommunications system.
The denomination xe2x80x9cmobile telecommunications systemxe2x80x9d refers generally to any telecommunications system which enables a wireless communication connection between a mobile station (MS) and the fixed parts of the system when the user of the mobile station is moving within the service area of the system. A typical mobile communications system is a Public Land Mobile Network (PLMN). The majority of mobile telecommunications systems in use at the time of filing this patent application belong to the second generation of such systems, a well-known example being the GSM system (Global System for Mobile telecommunications). The invention applies mostly to the next or third generation of mobile telecommunications systems. A system known as the UMTS (Universal Mobile Telecommunications System), which currently undergoes standardisation, is used as an example.
In third generation systems the concepts of a bearer and a service are introduced. A bearer generally corresponds to the older concept of a traffic channel, defming for example the user data rate and Quality or Service (QoS) that will be provided by the system for transferring information between a mobile station and some other part of the system. For example a bearer between the mobile station and a base station is a radio bearer and a bearer between a radio network controller and a core network is an Iu bearer (the interface between a radio network controller and a core network is called the Iu interface). A service is something that necessitates information transfer between a mobile station and the fixed parts of the system, like a phone call or the transfer of a text message. A major task for the operation of a third generation mobile telecommunications system is to manage (set up, keep up and tear down as necessary) the bearers so that each requested service can be provided to the mobile stations without wasting the available bandwidth. Some of the problems of bearer management will be illustrated in the following by referring to packet-switched data transmission finctions, where one of the most difficult tasks is to provide a truly reliable QoS for each user. The general packet radio service (GPRS) is a new service to the GSM system, and is one of the objects of the standardization work of the GSM phase 2+ and UMTS at the ETSI (European Telecommunications Standards Institute). The GPRS operational environment comprises one or more subnetwork service areas, which are interconnected by a GPRS backbone network. A subnetwork comprises a number of packet data service nodes (SN), which in this application will be referred to as serving GPRS support nodes (SGSN), each of which is connected to the mobile telecommunications system (typically to a base station through an interworking unit) in such a way that it can provide a packet service for mobile data terminals via several base stations, i.e. cells. The intermediate mobile communication network provides packet-switched data transmission between a support node and mobile data terminals. Different subnetworks are in turn connected to an external data network, e.g. to a public switched data network (PSDN), via GPRS gateway support nodes GGSN. The GPRS service thus allows to provide packet data transmission between mobile data terminals and external data networks when the appropriate parts of a mobile telecommunications system function as an access network.
In order to access the GPRS services, a MS shall first make its presence known to the network by performing a GPRS attach. This operation establishes a logical link between the MS and the SGSN, and makes the MS available for SMS (Short Message Services) over GPRS, paging via SGSN, and notification of incoming GPRS data. More particularly, when the MS attaches to the GPRS network, i.e. in a GPRS attach procedure, the SGSN creates a mobility management context (MM context). Also the authentication of the user is carried out by the SGSN in the GPRS attach procedure. In order to send and receive GPRS data, the MS shall activate the packet data address that it wants to use, by requesting a PDP activation procedure (Packet Data Protocol). This operation makes the MS known in the corresponding GGSN, and interworking with external data networks can commence. More, particularly a PDP context is created in the MS and the GGSN and the SGSN. The PDP context defines different data transmission parameters, such as the PDP type (e.g. X.25 or IP), PDP address (e.g. X. 121 address), quality of service (QoS) and NSAPI (Network Service Access Point Identifier). The MS activates the PDP context with a specific message, Activate PDP Context Request, in which it gives information on the TLLI, PDP type, PDP address, required QoS and NSAPI, and optionally the access point name (APN).
The quality of service defines how the packet data units (PDUs) are handled during the transmission through the GPRS network. For example, the quality of service levels defmed for the PDP addresses control the order of transmission, buffering (the PDU queues) and discarding of the PDUs in the SGSN and the GGSN, especially in a congestion situation. Therefore, different quality of service levels will present different end-to-end delays, bit rates and numbers of lost PDUs, for example, for the end users.
For each PDP address a different QoS may be requested. For example, some PDP addresses may be associated with E-mail that can tolerate lengthy response times. Other applications cannot tolerate delay and demand a very high level of throughput, interactive applications being one example. These different requirements are reflected in the QoS. If a QoS requirement is beyond the capabilities of a PLMN, the PLMN negotiates the QoS as close as possible-to the requested QoS. The MS either accepts the negotiated QoS, or deactivates the PDP context.
Current GPRS QoS profile contains five parameters: service precedence, delay class, reliability, and mean and peak bit rates. Service precedence defines some kind of priority for the packets belonging to a certain PDP context. Delay class defines mean and maximum delays for the transfer of each data packet belonging to that context. Reliability in turn specifies whether acknowledged or unacknowledged services will be used at the protocol layers where such alternatives are availablexe2x80x94examples in the known systems are the LLC (Logical Link Control) and RLC (Radio Link Control) layers. In addition, it specifies whether protected mode should be used in case of unacknowledged service, and whether the GPRS backbone should use TCP or UDP to transfer data packets belonging to the PDP context. Furthermore, these varying QoS parameters are mapped to a number of QoS levels available at certain protocol layers.
The known aspects of bearer management and QoS mapping are usually associated with the LLC layer. It has been proposed that the LLC layer should be omitted from future wireless packet-switched communication systems, but the following considerations are in any case useful in understanding the background of the invention. FIG. 1 illustrates the operation of a known LLC protocol layer 101 in a known Mobile Station (MS) or Serving GPRS Support Node (SGSN). Block 102 represents the known lower layer (RLC/MAC; Radio Link Control/Media Access Control) functions that are needed below the LLC layer 101 in a mobile station. Correspondingly block 103 represents the known lower layer (BSSGP; Base Station Subsystem GPRS Part) finctions that are needed below the LLC layer 101 in a SGSN. The interface between the LLC layer 101 and the RLC/MAC layers is called the RR interface and the interface between the LLC layer 101 and the BSSGP layers is called the BSSGP interface.
Above the LLC layer there are the known GPRS Mobility Management functions 104, Subnetwork Dependent Convergence Protocol (SNDCP) finctions 105 and Short Messages Services finctions 106 that belong to Layer 3 in the layered protocol structure that is employed. Each one of these blocks has one or more interfaces with the LLC layer 101, connecting to its different parts. The Logical Link Management Entity 107 has an LLGMM control interface (Logical Link-GPRS Mobility Management) with block 104. Mobility management data is routed through a LLGMM data interface between block 104 and the first Logical Link Entity 108 of the LLC layer. The second 109, third 110, fourth 111 and fifth 112 Logical Link Entities connect to block 105 through the corresponding interfaces; according to the QoS levels handled by each of the Logical Link Entities the interfaces are known as QoS 1, QoS 2, QoS 3 and QoS 4. The sixth Logical Link Entity 113 of the LLC layer connects to block 106 via an LLSMS interface (Logical Link-Short Messages Services). The Service Access Point Identifiers or SAPIs of the first 108, second 109, third 110, fourth 111, fifth 112 and sixth 113 Logical Link Entities are respectively 1, 3, 5, 9, 11 and 7. Each one of them is connected inside the LLC layer to a multiplexing block 114, which handles the connections through the RR interface to block 102 in a mobile station or the connections through the BSSGP interface to block 103 in an SGSN.
The connection between the multiplexing block 114 and the lower layer block 102 in the MS may be described as a xe2x80x9ctransmission pipexe2x80x9d. Because all data flows between the upper parts of the LLC layer and the lower layers 102 go through the same multiplexing procdure 114 and the same transmission pipe, the maximum bit rate and mean bit rate parameters of the available QoS profile relate to this transmission pipe. However, the GPRS standard does not define this relation clearly. The QoS profile is negotiated during the PDP activation procedure referred to above, and it can not be changed after initial assignment. For example it is not possible to change the maximum bit rate and/or the mean bit rate according to the momentary needs of the user otherwise than below a certain maximum negotiated at the activation of the PDP context. Although this problem has been described in context of GPRS services, it applies generally to all such mobile telecommunications systems where different services will require different QoS profiles but their relation to the information exchange between the Logical Link Control layer and the lower layers have been poorly and/or inflexibly defined.
It is thus an object if this invention to provide a method and a system for managing the bearers in a mobile telecommunications system so that the changing data transmission needs of a user during a connection may be accounted for.
The objects of the invention are fulfilled by having several parallel transmission pipes, corresponding to different QoS profiles, within the layered protocol structure and forwarding the QoS needs of the services and/or applications to a Call Management entity which then increases or decreases the capacity of each transmission pipe according to need.
It is characteristic to a method according to the present invention that it comprises the steps of
a) demultiplexing a flow of data to be transmitted coming from the L3 layer into a number of component data flows, each component data flow having a certain Quality of Service requirement,
b) arranging the component data flows into groups where the Quality of Service requirement of each component data flow in a group is similar to the Quality of Service requirements of the other component data flows belonging to the same group,
c) multiplexing the component data flows groupwise into multiplexed data flows and
d) outputting the multiplexed data flows to the MAC layer.
The invention also applies to a telecommunication device having the characteristic means for
demultiplexing a flow of data to be transmitted coming from the L3 layer of a protocol stack into a number of component data flows, each component data flow having a certain Quality of Service requirement,
arranging the component data flows into groups where the Quality of Service requirement of each component data flow in a group is similar to the Quality of Service requirements of the other component data flows belonging to the same group,
multiplexing the component data flows groupwise into multiplexed data flows and
outputting the multiplexed data flows to the MAC layer of said protocol stack.
According to the invention the protocol layers including the known Layer 3 and the known MAC layer are structured so that
an incoming data flow from Layer 3 is demultiplexed into its potential component data flows which may have mutually different QoS requirements,
the resulting component data flows are processed and
the processed component data flows originating from different incoming data flows but having similar QoS requirements are multiplexed together before directing them further to the MAC layer.
The QoS requirements that can be taken into account are mainly related to the expected delay and the used coding. The invention does not restrict the choice of network element to which the invention is applied, but it should be noted that not all network elements include all protocol layers. A certain protocol layer in a certain mobile station or a fixed part of the network has in most cases a peer entity in some other device it is communicating with. According to a preferred embodiment of the invention the multiplexed bitstream of data flows having similar QoS requirements will be conveyed through the whole mobile telecommunications system and demultiplexed again only at the PDAN (Packet Data Access Node) or the WMSC (Wireless/Mobile Switching Centre) from which the component data flows continue in a network where their specific QoS requirements are independently accounted for.